Jacket/baked potato with butter, or with coleslaw if you can get it. That's what I used to eat a lot of, with a tzatziki-like topping of cucumber, yoghurt, and garlic. All cheap ingredients but really tasty!
Buy a big bag of frozen mixed veggies, some rice and some eggs, and you can have a basic vegetable fried rice for good protein and vegetables.
If you like soup, save any scraps you have from prepping vegetables (like broccoli stems, carrot peels and ends, bits of vegetables that are going a bit soft so you don't want to eat them raw. Freeze them and then when you've got a decent amount, make a scrap soup by mixing them with a stock cube , water, and any herbs or spices you have. Blend it up and you'll have a meal for a few days.
You can make a killer risotto so easily. There's definitely purists out there who would have my head. But you could go as simple as some Arborio rice, fried in a pan with some oil for a few minutes, and then add in like some stock with a 3:1ish ratio with the rice (You can play this by ear).
Add some parmesan at the end and bam - pretty delicious meal right there. You can add Mushroom, Peas, Chroizo, Bacon, etc for some more flavour. I also can't recommend Thyme enough, realllly brings it up a notch.